1. Field of the Invention
The present invention relates to a wireless LAN network, specifically, to load control for an access point included in the wireless LAN network.
2. Description of the Related Art
A general WLAN (Wireless Local Area Network) network is configured so that a WLAN-AP (Access Point) connected to a higher-level network on a wire line accommodates a WLAN terminal on a wireless line to allow connection between the WLAN terminal and the higher-level network. Examples of the higher-level network are 3GPP (3rd Generation Partnership Project) network, ISP (Internet Services Provider) network, Internet, Intranet, and the like.
The WLAN network adopts the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) method for access control in a wireless section. This CSMA/CA method controls plural WLAN terminals to share the same wireless channel in a time-division mode.
In the WLAN network of such a configuration, a band usage rate may increase and the throughput may decrease because of the increase in the number of users (the number of WLAN terminals) connected to the WLAN-AP and the concentration of traffic on a certain period. The decrease of the throughput adversely affects services in terms of the increase of delay.
In consideration of the decrease of throughput, a bottleneck for a throughput is likely to exist in a wireless section. This is because the wired section between a WLAN-AP and a higher-level network is generally provided with a relatively large transmission capacity, while a wireless section between a WLAN-AP and a WLAN terminal is provided with only a limited band. This is attributed to the nature of wireless communication such that limited resource provided to a WLAN network should be effectively utilized because of limited radio frequency.
One of the causes for a decrease in throughput is the reduction of resources in a wireless channel because many WLAN terminals are connected under a single WLAN-AP. In the CSMA/CA method, plural WLAN terminals can not access a target wireless channel at the same time. If many WLAN terminals use a wireless channel in a time-division mode, the time allowed for one of the WLAN terminals to have an access may be shortened. This also causes the throughput to decrease.
Even when a smaller number of WLAN terminals are connected to a WLAN-AP, the throughput may decrease because some WLAN terminals among them utilize a rich service. A rich service is a service which needs real-timeness and a band above a certain level, such as VoIP and Video. A real-time rich service such as a streaming service of VoIP and Video needs to secure high-rate and stable throughput to provide a service which is stable in quality. Thus, a rich service greatly influences the throughput of a WLAN network.
In recent years, because the market related to the WLAN has expanded, the area in which WLAN service is provided has also expanded, and the number of WLAN terminals utilizing the WLAN service has increased. As the number of WLAN terminals increases, there is a concern that the WLAN network may be overloaded, which may reduce throughput and degrade service quality and the performance of the network connection.
The WLAN network is required to provide various sizes of service areas according to the locations in which the WLAN network is applied. To address this, the required size of service area is formed by positioning the required number of WLAN-APs close to each other. Generally, because a WLAN terminal can move, it may move from a coverage area of one WLAN-AP to a coverage area of another WLAN-AP. At that time, the WLAN terminal is handed over or reconnected to the other WLAN-AP to continue communication.
In the WLAN network in which plural WLAN-APs are thus located close to each other, it can be expected that the overload state will be alleviated and that good overall service quality will be maintained by distributing and balancing the loads on each WLAN-AP.
Thus, a technique is proposed in which a management apparatus is disposed for collectively managing the congested state of plural WLAN-APs, which in turn control WLAN terminals by taking into account the congestion. Japanese Patent Laid-Open No. 2006-067103 (hereinafter, referred to as Document 1) discloses such a technique in which a management server manages the number of WLAN terminals connected to each of plural WLAN-APs, and instructs a newly connected WLAN terminal to connect to the best WLAN-AP.
According to the technique disclosed in the above Document 1, regardless of whether or not the WLAN network is in a state where the congestion should be alleviated, the management server determines the best WLAN-AP based on the state of each WLAN-AP, etc. and notifies it to a WLAN terminal whenever the WLAN terminal is newly connected. Thus, there is such a problem that, as the number of WLAN-APs under the management server and/or the number of WLAN terminals which try to connect to WLAN-APs increase, the amount of processing in the management server that is needed to make a determination and carry out notification also increases.